The embodiments described herein relate generally to fluid systems and, more particularly, to methods and apparatus that facilitate erosion detection of valves in steam systems.
At least some steam turbines are coupled to steam generators that include at least one fossil fuel-fired boiler and/or at least one heat recovery steam generator (HRSG). Boilers and HRSGs include tubing that converts water to steam. The steam turbine is coupled to the boiler/HRSG via steam piping. Some known steam turbines include steam turbine inlet isolation valves and steam turbine control valves. Such isolation and control valves may be combined into a single valve assembly. Steam is channeled to the steam turbine via a steam transport system that includes the steam piping, isolation valves, and control valves.
Many known steam piping systems between the steam boilers and HRSGs include metallic piping and the tubing in the boilers and HRSGs is also metallic. The metallic, e.g., ferrous, piping and tubing is subject to exfoliation of solid particles, e.g., magnetite, from the interior walls of the piping and tubing into and through the steam transport system. The solid particles become entrained within the steam channeled from the boilers/HRSGs to the steam turbine and impact the components in the steam transport path, thereby introducing an erosion mechanism to those components, wherein the mechanism is typically referred to as solid particle erosion. Over time, solid particle erosion may induce accelerated wear of steam turbine components, including steam valves, e.g., valve stems. Increased wear of steam valve stems due to solid particle erosion results in a decrease of plant efficiency, and extended wear may result in lower reliability and availability due to an increased frequency of steam turbine outages to inspect and/or repair the steam valves. Moreover, most known inspection procedures require physical disassembly of the steam valves to visually inspect the stem for material losses due to erosion. The decrease in turbine performance and the increase in maintenance activities result in an increase in operating costs.